Matrix retainer



July 14, 1 A. M. PRATT MATRIX RETAINER Filed May 17, '1962 United States Patent 3,140,544 MATRIX RETAINER Alexander M. Pratt, 328 E. 75th St, Chicago 19, Ill.

Filed May 17, 1962, Ser. No. 195,520

Claims. (Cl. 3263) This invention relates generally to the art of dentistry, more particularly to dental matrices and especially to retainers therefor.

It is common practice to use a ribbon-type matrix in forming and hardening amalgam, porcelain and plastic fillings. These matrices are also used as a protective covering for the tooth adjacent a tooth in which a Class II cavity is being excavated. In addition, such matrices are usefully employed in connection with the making of wax impressions for gold inlays on teeth of the bicuspid or molar type. Conventionally, a dental matrix comprises a flat strip of thin flexible spring steel of a width approximately equal to the height of a tooth and of a length approximating three inches. The strip is adapted to be looped for encircling the tooth which is to be worked on, and the ends of the strip are brought together and tensioned by a specially formed holder known as a retainer.

The matrix retainers heretofore available have been, because of their method of operation, rather sizable and clumsy devices uncomfortable for the patient to retain in his mouth. In an attempt to overcome this problem, crimpable locking elements known as crimp locks have been devised to preserve tension drawn. in the matrix by a retainer, the crimp lock being positioned between the retainer and the tooth being worked upon prior to manipulation of the retainer to draw tension into the matrix. However, these crimp locks must be pried apart or otherwise disengaged from the matrix in order to eliect removal of the matrix from the tooth and from the mouth of the patient. Objectionable discomfort has resulted from this latter operation.

Moreover, the prior art schemes of applying a ribbontype matrix to a tooth involve a considerable number of manipulations which must be performed within the mouth of the patient. The resultant time period during which appliances and the hands of the dentist must remain in the mouth of the patient cause considerable fatigue and discomfort to both.

Therefore, an important object of the present invention is to provide a new and improved dental matrix retainer.

Another object of the invention is to provide a matrix retainer having a size and shape which render it both convenient for the dentist to fit in place and comfortable for the patient to receive and retain in his mouth.

Still another object of the invention is to provide a matrix retainer which facilitates preservation of a dry area surrounding the tooth being repaired.

And yet another object of the invention is to provide a dental matrix retainer which quickly and easily releases the matrix for removal.

A further object of the invention is to provide a matrix retainer which achieves a close fit of the matrix around the tooth.

A still further object of the invention is to provide an improved dental matrix and cooperating retainer.

These and other objects and features will become more apparent upon a reading of the following descriptions.

A structure in accord with the invention includes a retainer body having rigidly spaced jaws adapted to receive the end portions of a looped matrix therebetween, one of the jaws including a pair of arms spaced apart to define a channel; matrix-retention means on one of the arms for securing the ends of the matrix in a posi- 3,140,544 Patented July 14, 1964 tive position; and a stud member progressively engaging a different one of the jaws to extend a terminal portion interjacent the arms for aggressively abutting the end portions of the matrix in order to draw tension therein.

The invention, both to its structure and mode of operation, will be better understood by reference to the following disclosure and drawing forming a part thereof, wherein:

FIG. 1 is a perspective view of a dental matrix attached to a tooth in the lower jaw by means of a retainer constructed in accordance with the present invention and showing use of the retainer in positioning an absorbent cotton roll;

FIG. 2 is an enlarged perspective view of the retainer illustrated in FIG. 1;

FIG. 3 is an enlarged cross-sectional View taken along the line 33 of FIG. 1;

FIG. 4 is a view taken along the line 44 of FIG. 3;

FIG. 5 is a perspective view in a different scale showing the shoe member used in the retainer of FIG. 2; and

FIG. 6 is a perspective view of a dental matrix constructed in accordance with the principles of the invention and shown in approximately actual size.

Referring now in detail to the drawing, specifically to FIG. 1, a dental matrix indicated generally by the numeral 10 will be seen attached to a tooth 12, a right lower bicuspid as shown. The matrix 10 is attached to the tooth 12 using a matrix retainer 14; and although the retainer 14 is illustrated in a labial position, it may equally well be disposed in a lingual position if desired. It will be noted that the retainer 14 is of a compact size, approximating the size of a tooth, and hence its retention in the patients mouth does not pose any substantial inconvenience. However, the retainer 14 is sufficiently large to act as an upstop for a cylindrical cotton absorbent member 16 of the type conventionally employed in dentistry for preserving a dry area surrounding a tooth being worked upon.

The dental matrix 10 comprises a thin, flexible band of tensilely strong material such as stainless steel; and in accordance with the present invention, as is well shown in FIG. 6, the matrix 10 is provided with a substantially straight longitudinal edge 18 and an opposite edge 20 which defines a relatively fiat curve. The edges 18 and 20 are arranged so that the width of the matrix 10 is a maximum at the midregion 22, the matrix tapering to its minimum width at the opposite end portions 24 and 26. For the purposes of the invention, edge 18 need not be perfectly straight but may take a slight curvature. It is important to note that the end portions 24 and 26 of the matrix are fashioned with spaced, longitudinally aligned apertures 28, the purposes of which will be described shortly.

Considering FIGS. 2-4, the matrix retainer 14 will be seen to comprise a generally C-shaped body 30 having parallel jaws 32 and 34 rigidly spaced apart by a plate 36 and a stem 37. Spacing of the jaws 32 and 34 permits the end portions of a looped matrix 10 to be passed therebetween. Moreover, jaw 32 is fashioned to include a pair of parallel arms, arms 38 and 40, which are spaced apart to define a channel 42.

In order to secure the ends of a matrix 10 in positive position relative to the retainer 14, the arm 38 is fashioned with a barb or prong 44 which is adapted to be received in selected apartures 28 in the matrix as is well indicated in FIG. 3. By virtue of the provision of two or more of the apertures 23 in each of the end portions 24 and 26 of the matrix, a certain amount of latitude is afforded in selecting the size of the loop which is formed in the central portion of the matrix for surrounding a tooth.

After the looped matrix has been fitted over a tooth, it is desired to draw tension into the matrix in order to make it to conform to the outline of the tooth. Accordingly, means are provided in the retainer 14 for drawing tension in the matrix 10; and these means include a stud member 46 having a threaded shank portion 48 and a head 50. The threaded shank portion 48 progressively engages a cooperatively threaded bore 52 formed in jaw 34, and the head 50 is fashioned with a diametral slot 54 and with a beveled, knurled, peripheral edge 56 for facility in turning the stud member 48 relative to the retainer body 30. When the stud member 46 is operated to draw tension into the matrix 10, the threads of the shank portion 48 react lockingly against the threads of bore 52 to secure a selected adjustment of the retainer 14.

With particular reference to FIG. 3, the arm 40 will be seen fashioned with a contoured surface 58, and the jaw 34 will be seen fashioned with an adjacently disposed extension 60 having a contoured surface 62 which converges with the surface 58 in order to fit the matrix 10 closely about the adjacent surface of tooth 12. It will be noted that the extension 60 and the arm 40 are closely spaced in order to maximize the fitting relationship between the matrix 10 and the tooth 12 which is encircled thereby.

That terminal portion of stud member 4-6 which is opposite head 5-0 is intended aggressively to abut the end portions of matrix which are disposed between arms 38 and 4%, upon progressive engagement of the stud member and the jaw 34. In compliance with the illustrated embodiment, the terminal portion of stud member 46 is provided with a rounded knob 64 having a constricted, annular waist 66. Furthermore, a shoe member 68 is coupled to the knob 64 for free rotation and limited relative axial movement. As is well shown in FIGS. 3 and 5, the shoe member 68 comprises an elongated plate having its opposite lateral edges turned inwardly to define a curved external surface 70 for abutment with the matrix 10. In addition, this arrangement of the shoe member 68 develops an internal channel 72 which is adapted to receive the knob 64, the channel 72 having suflicient trans verse dimension to permit free rotation of the knob while the inwardly curved lateral edges of the shoe member reside in the constricted waist 66 of the knob whereby to limit relative axial movement of the parts.

Considering FIG. 4, the length of arms 38 and 40, and thereby the length of the channel 42 formed therebetween, will be observed to exceed the width of matrix 10. Furthermore, the shoe member 68 is to be noted as approximating the length of that channel. Thus, tensioning forces applied to the end portions of the matrix by means of the stud member 46 are applied across the total width of the matrix in order to prevent distortion thereof and in order to insure easy extraction of the matrix from the retainer 14.

As will be noted with reference to FIG. 3, the dimension of the jaws 32 and 34 which is taken generally transversely of channel 42 and of stud member 46 approximates the diameter of the absorbent member 16. Accordingly, when the retainer 14 is operated to tension the matrix It), the retainer will be fixed relative to the tooth 12 in which position it is capable of acting as an upstop for the absorbent member placed therebeneath. The retainer 14 thereby acts to preserve a dry area surrounding the tooth 12.

For purposes of aifording a more complete understanding of the invention, it is advantageous now to provide a.

functional description of the mode in which the component parts cooperate.

Assuming that a tooth has been selected for repair, such as by the making of an amalgam filling, a matrix 10 will be looped so that its opposite end portions abut each other with two of the apertures 28 aligned to form a passageway. The martix 10, thus configurated, is then inserted between the jaws 32 and 34 of the retainer 14, and the barb 44 is passed through the aligned apertures 28, these operations being performed outside of the mouth of the patient. Next, the stud member 46 is turned down until the shoe member 68 contacts the end portions 24 and 26 of the matrix whereupon the looped portion of the matrix may be placed about the tooth to be worked upon and a slight amount of tension may be drawn into the matrix to hold it in place. The fingers of the dentist, gripping the knurled edge of head 50, are readily employed in applying this initial tension.

Thereafter, a screw driver or other suitable, fiat bladed tool may be inserted in the slot 54 for further driving the stud member and the shoe member 68 attached thereto against the abutted end portions of the matrix. As will be recognized, the barb 44 and the tooth 12 define two relatively fixed positions of the matrix between which it may be tensioned.

Upon completion of the work on the tooth 12, the stud member 46 may be turned out of the retainer 14 in the same manner in which it was turned in; and because shoe member 68 confronts the total width of the end portions of the matrix, no distortions, such as ridges or bumps, are formed in the matrix during tensioning. Hence, loosening of the stud member 46 simultaneously releases the tension on the matrix, permitting its easy removal from the tooth 12 and easy extraction of the matrix from the retainer 14.

The various components of the retainer 14 are intended to be fabricated from a suitable metal so that the retainer may be easily sterilized by either the wet or the dry method.

The specific examples herein shown and described are to be considered as being primarily illustrative. Various changes in structure will, no doubt, occur to those skilled in this art; and these changes are to be understood as forming a part of this invention insofar as they fall within the spirit and scope of the appended claims.

The invention is claimed as follows:

1. A retainer for dental matrices comprising: a retainer body having rigidly spaced jaws adapted to receive the end portions of a looped matrix transversely therebetween, one of said jaws including means defining a channel for accommodating the terminal portion of a stud member; matrix-retention means on an edge portion of said one jaw for securing the ends of said matrix in a positive position; a stop surface on the opposite edge portion of said one jaw for use in positioning said retainer relative to a tooth encircled by the looped portion of said matrix, said channel being disposed intermediate said stop surface and said matrix-retention means; and a stud member progressively engaging a different one of said jaws to extend a terminal portion into said channel for aggressively abutting the end portions of said matrix in laterally engaged relationship whereby to urge the engaged portions of said matrix into said channel and thereby draw tension into the looped portion of said matrix.

2. A retainer for dental matrices comprising: a retainer body having rigidly spaced jaws adapted to receive the end portions of a looped matrix therebetween, one of said jaws including a pair of arms spaced apart to define a channel: matrix-retention means on one of said arms for securing the ends of said matrix in a positive position; a stud member progressively engaging a different one of said jaws to extend a terminal portion interjacent said arms for aggressively abutting the end portions of said matrix in order to draw tension therein; and a shoe member coupled to said terminal portion for free rotation and limited relative axial movement therewith.

3. A retainer according to claim 2 wherein said shoe has an elongated curved surface abuttable with said matrix, wherein the length of said channel exceeds the width of conventional dental matrix, and wherein the length of said shoe member approximates the length of said channel whereby tensioning forces are applied across the total width of said matrix to prevent distortion thereof and thereby insure easy extraction from said retainer.

4. A retainer according to claim 2 wherein the other of said arms and said ditferent jaw are closely spaced to maximize the fitting relationship between a said matrix and a tooth encircled thereby.

5. A retainer according to claim 1 wherein said stud 5 member is provided with a threaded portion and wherein said difi'erent jaw is provided with a cooperatively threaded bore for receiving said threaded portion whereby threadedly engaged portions of said different jaw and said stud member react lockingly to tension drawn in said matrix for 10 securing a selected adjustment of said retainer.

References Cited in the file of this patent UNITED STATES PATENTS Curran May 8, 1928 Holfmann et al. July 8, 1941 Muller Nov. 7, 1950 Hazlett Apr. 10, 1962 FOREIGN PATENTS Germany Feb. 23, 1953 Germany May 25, 1961 

1. A RETAINER FOR DENTAL MATRICES COMPRISING: A RETAINER BODY HAVING RIGIDLY SPACED JAWS ADAPTED TO RECEIVE THE END PORTIONS OF A LOOPED MATRIX TRANSVERSELY THEREBETWEEN, ONE OF SAID JAWS INCLUDING MEANS DEFINING A CHANNEL FOR ACCOMMODATING THE TERMINAL PORTION OF A STUD MEMBER; MATRIX-RETENTION MEANS ON AN EDGE PORTION OF SAID ONE JAW FOR SECURING THE ENDS OF SAID MATRIX IN A POSITIVE POSITION; A STOP SURFACE ON THE OPPOSITE EDGE PORTION OF SAID ONE JAW FOR USE IN POSITIONING SAID RETAINER RELATIVE TO A TOOTH ENCIRCLED BY THE LOOPED PORTION OF SAID MATRIX, SAID CHANNEL BEING DISPOSED INTERMEDIATE SAID STOP SURFACE AND SAID MATRIX-RETENTION MEANS; AND A STUD MEMBER PROGRESSIVELY ENGAGING A DIFFERENT ONE OF SAID JAWS TO EXTEND A TERMINAL PORTION INTO SAID CHANNEL FOR AGGRESSIVELY ABUTTING THE END PORTIONS OF SAID MATRIX IN LATERALLY ENGAGED RELATIONSHIP WHEREBY TO URGE THE ENGAGED PORTIONS OF SAID MATRIX INTO SAID CHANNEL AND THEREBY DRAW TENSION INTO THE LOOPED PORTION OF SAID MATRIX. 